that farm should work nice

a few things tho...
I would replace the 'dry land loam' in the foraging area with Clay Aggregate, otherwise the ants will more than likly build their nest in it, also the 'regular dirt' and dry sand are more than likly going to end up being nested in, unless you use a very thin layer, maybe 5mm, this should be no problem for the grass to grow in...however...
grass, i'm not sure you realize how long grass grows in the wild, it grows very long! yes you can cut it, but you dont really want bits of dead grass in the tank, it will rot slowly, with no other insects to clean it up, unless you are going to look into some insects to include with the ants
30x30x30cm is to small imo, the nesting area can be about this, and the foraging area needs to be about the same, so double that to 60cm wide, and it should be ok
remeber to include connoctors incase the colony gets to big, or somthing happens that means u need to move your colony to a new setup
how are you planning on sealing the wood from the water? even a tiny amount of water will warp the wood, crack your glass and lead to a bit of a disaster...